Topic: Bundle Branch Blocks and Ventricular Rhythms
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Idioventricular rhythms are rhythms where the initiating pacemaker is ectopically located in the ventricles themselves instead of the SA node or AV node. ECTOPY is an abnormal beginning point--a site of ectopic origination--of an electrical impulse within the cardiac muscle.
These ventricular arrhythmias range from asymptomatic premature ventricular beats to ventricular fibrillation. Patients at risk are those with heart failure and cardiomyopathy. There are 2 main categories of ventricular arrhythmias:
--Sustained ventricular tachycardia.
--Ventricular premature beats (VPBs)
--Nonsustained ventricular tachycardia (NSVT)
--Accelerated idioventricular rhythm (AIVR).
Ventricular Premature Beats (VPBs)
VPBs occur in up to 95% of those with heart failure. In those with MI, however, they signify an increased risk of death. (In non-ischemic cardiomyopathy they are not.) Because of this risk, they should be suppressed with medication.
Symptoms of VPBs: Palpitations. Beta-blockers can usually control their frequency.
Nonsustained Ventricular Tachycardia (NSVT)
NSVT "runs" (3 or more consecutive ventricular beats within a heart rate of 100-140 beats/min) occur in up to 80% of those with heart failure and cardiomyopathy.
- The rate of an idioventricular rhythm is usually 20-40 beats per minute.
- An accelerated idioventricular rate is higher, > 40 beats/minute.
These rhythms show no relationship between the QRS complexes and the preceding atrial cardiac activity.
- P waves are often absent or abnormal and
- QRS complexes are wide.
At least three consecutive beats are required to make a rhythm or “run.”